aerobic or completely mixed feeding. In the case of anaerobic plug
flow feeding through the granule bed, most of these factors (like
high settling pressure, shear, high DO etc.) become less relevant,
although not irrelevant, during start-up (de Kreuk et al., 2005).
Anaerobic feeding selects for relatively slow growing bacteria such
as PAOs, that convert the easy degradable COD under anaerobic
conditions into storage polymers, resulting in smooth and compact
biofilms (Van Loosdrecht et al., 1997). The plug flow feeding
furthermore ensures high substrate concentrations near the
granule surface allowing substrate to diffuse through the entire
granule, further contributing to the formation of stable, compact
and dense granular biomass.